Aircraft takeoff abort indicator

ABSTRACT

An apparatus for indicating to the pilot of an aircraft whether to abort a takeoff because of subnormal acceleration during the takeoff run includes: an elongated chart of the normal takeoff acceleration versus takeoff time for the aircraft for a particular set of conditions; a warning indicator; means adapted to scan the chart and responsive to subnormal takeoff acceleration for actuating the warning indicator. The chart is movable linearly and is provided with a conductive area representing the subnormal takeoff acceleration versus takeoff time relationship for the aircraft and a particular set of conditions. The actuating means for the warning indicator includes a contact engageable with such conductive area that is movable relative to the actual aircraft acceleration. An aircraft utilizing the apparatus is provided with a set of charts covering different airports, aircraft weights, wind and barometric pressure and other variable conditions that affect takeoff requirements.

United States Patent [:91

Hansen AIRCRAFT TAKEOFF ABORT INDICATOR [76] Inventor: Raymond J.Hansen, PO Box 727.

Sanger, Calif. 93657 [22] Filed: Mar. 16, 1973 [21] Appl. N0.: 342,155

Related U.S. Application Data [63] Continuation-in-part of Ser. No.224,211, Feb, 7,

1972, Pat. No. 3,738,165.

[52] U.S. Cl. 73/178 T; 340/27 R [51] Int. Cl G0lc 21/10 [58] Field ofSearch 73/178 T; 346/7;

116/129 R; 340/27 R, 27 SS, 27 NA [56] References Cited UNITED STATESPATENTS 2,695,121 1 11/1954 Guttwein et a1. i. 346/7 3,738,165 6/1973Hansen 73/178 T Primary Examiner-Donald O. Woodiel Arrorney, Agent, orFirmOwen, Wickersham & Erickson [4 1 Aug. 5, 1975 I 5 7] ABSTRACT Anapparatus for indicating to the pilot of an aircraft whether to abort atakeoff because of subnormal acceleration during the takeoff runincludes: an elongated chart of the normal takeoff acceleration versustakeoff time for the aircraft for a particular set of conditions; awarning indicator; means adapted to scan the chart and responsive tosubnormal takeoff acceleration for actuating the warning indicator. Thechart is movable linearly and is provided with a conductive arearepresenting the subnormal takeoff acceleration versus takeoff timerelationship for the aircraft and a particular set of conditions. Theactuating means for the warning indicator includes a contact engageablewith such conductive area that is movable relative to the actualaircraft acceleration. An aircraft utilizing the apparatus is providedwith a set of charts covering different airports, aircraft weights, windand barometric pressure and other variable conditions that affecttakeoff requirements.

4 Claims, 6 Drawing Figures AIRCRAFT TAKEOFF ABORT INDICATOR BACKGROUNDOF THE INVENTION This is a continuation-in-part of Ser. No. 224,211filed Feb. 7, 1972 now US. Pat. No. 3,738,165.

The present invention relates in general to the problems involved indeciding when to abort takeoff of an aircraft in the event thatconditions precluding a safe takeoff develop and, more particularly, toan apparatus for indicating when to abort the takeoff.

As is well known, a safe takeoff requires the aircraft to achieve flyingspeed far enough from the end of the runway to enable the aircraft toclear any obstacles which may be present. For every takeoff, there is asocalled abort point. If for some reason the aircraft does not increaseits airspeed as rapidly as it should between the start of the takeoffrun and the abort point, the takeoff can be aborted safely at any pointon the runway up to the abort point. If the decision to abort is delayedtoo long after the aircraft passes the abort point, it may not bepossible to abort the takeoff safely.

Frequently, the pilot of the aircraft is required to make the decisionwhether to abort as the result of his own visual observations of theairspeed indicator of the aircraft and the position of the aircraft onthe runway. This is undesirable for various reasons. For one thing,requiring the pilot to make the necessary visual observations distractshim from other duties he must perform during takeoff, and represents anintolerable additional burden in large commercial aircraft. Secondly, itis well known that airspeed indicators are often very inaccurate at lowspeeds, so that an airspeed indicator does not provide the pilot with areliable guideline. Further, visual observations of the position of theaircraft on the runway cannot be made under conditions of poorvisibility, such as those resulting from fog, rain, snow, and the like.Under such condition, the pilot may have no real idea where he is on therunway.

In view of problems of the foregoing nature, various systems have beendeveloped for indicating automatically whether to abort a takeoff, andwhen. Prior systems with which I am familiar rely on measuring eitherthe airspeed of the airplane, or its ground speed. In either case, ifthe speed is not sufficiently high by the time the aircraft reaches theabort point for a particular set of conditions, the system actuates awarning indicator. Prior systems utilizing airspeed measurements tend tobe unreliable because, as previously indicated, airspeed indicators areinherently inaccurate at low speeds. Further, such apparatuses requireconnections to the airspeed indicating system of the aircraft, or aseparate airspeed indicating system. Prior apparatuses relying on theground speed of the aircraft require a special ground-speed-sensingwheel, or a connection to one of the wheels of the aircraft itself.Consequently, apparatuses of this type are relatively complex.

SUMMARY AND OBJECTS OF INVENTION The primary object of the invention isto provide an abort indicating system which avoids the foregoing andvarious other difficulties of other systems by relying solely on theacceleration of the aircraft during its takeoff run, and which activatesa warning device or indicator if the takeoff acceleration is inadequateto achieve a speed high enough for a safe takeoff. In other words, theinvention determines if the proper takeoff speed has been attainedsolely by measuring acceleration with respect to time.

More particularly, an important object of the invention is to provide anaircraft abort indicating system which includes: a chart of normaltakeoff acceleration versus takeoff time for the aircraft under aparticular set of conditions; a warning indicator; and means adapted toscan the chart, and responsive to subnormal takeoff acceleration of theaircraft, for actuating the warning indicator. A related object is toprovide each aircraft with a set of interchangeable charts for differentaircraft weights, different runways (which take care of variations inrunway altitudes, runway slopes, and the like), different windconditions, different barometric pressure conditions, and the like.Thus, the pilot merely selects the chart corresponding to, or mostnearly corresponding to, the particular set of conditions with which heis faced for takeoff.

An important advantage of the foregoing is that the abort indicatingsystem, relying only on aircraft acceleration during takeoff, can be arelatively simple, selfcontained unit requiring no connections toexternal devices, such as airspeed indicators, ground speed sensors, orthe like.

The invention may be summarized as including, and an important object isto provide an abort indicator which comprises; a chart carrier; a charton the carrier of normal takeoff acceleration versus takeoff time forthe aircraft for a specific set of conditions; carrier driving means fordisplacing the takeoff time scale on the chart past a reference point;an acceleration indicator at the reference point and adapted to indicateon the chart the actual takeoff acceleration of the aircraft versustakeoff time; acceleration responsive means responsive to the actualtakeoff acceleration of the aircraft for actuating the accelerationindicator; a warning indicator; and actuating means adapted to scan thenormal takeoff acceleration versus takeoff time relationship on thechart, and responsive to subnormal takeoff acceleration of the aircraft,for actuating the warning indicator.

Another ojbect is to provide an abort indicator wherein the chart has aconductive area representing the subnormal takeoff acceleration versustakeoff time relationship for the particular aircraft and set ofconditions, and wherein the actuating means for the warning indicatorincludes a contact engageable with the conductive area.

Yet another object is to provide on the chart another conductive areaextending across the chart at a point on the time scale indicating themaximum permissible takeoff time without aborting, thereby providing anadditional safety factor.

Still another object is to provide an abort indicator wherein thecarrier is linearly movable and wherein the chart having a rectangularshape has a vertical takeoff acceleration scale and a takeoff time scalein the horizontal direction of chart movement.

The foregoing objects, advantages, features and results of the presentinvention, together with various other objects, advantages, features andresults thereof which will be evident to those skilled in the art in thelight of this disclosure, may be achieved with the exemplary embodimentsof the invention illustrated in the accompanying drawing and describedin detail hereinafter.

DESCRIPTION OF THE DRAWING In the drawing:

FIG. I is a schematic front view of the abort indicator of theinvention;

FIGv 2 is a vertical sectional view of one physical embodiment of theabort indicator;

FIG. 3 is an enlarged fragmentary view taken as indicated along line 3-3of FIG. 2;

FIG. 4 is an elevational view taken along line 4-4 of FIG. 3;

FIG, 5 is a view somewhat similar to FIG. 2 but showing an alternativeembodiment; and

FIG. 6 is another alternative embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF INVENTION In thedrawing, the takeoff abort indicator embodying the principles of thepresent invention is designated generally by the numeral I0 and is shownin FIGS. 2 and 3 as including a housing 12 having a base 14 covered onits lower side with a layer of friction material. With thisconstruction. the abort indicator may be used in any airplane simply byplacing the housing 12 on a suitable substantially horizontal supportingsurface. After takeoff, the unit can be stored in any suitable locationin the airplane. This construction is particularly suitable for use inrelatively small aircraft, especially private aircraft. For largecommercial aircraft, the abort indicator I0 may be built into, orpermanently installed on, a suitable instrument panel of the aircraft.In either event, the device is so oriented that the direction of takeoffacceleration of the aircraft is as indicated by the arrow [8 in FIG. 2.

The abort indicator 10 comprises an acceleration chart or card holder 16comprised of a rigid backplate or board and U" shaped flanges extendinghorizontally across the top and bottom of the backplate. The holder isattached to the case housing I2 by suitable flange members 19 located atopposite ends of the backplate. A friction roller 20 which may be madeof a soft rubber material mounted on a shaft 21 is driven at a constantrate by an electric motor 22 through a level gear train 24, and itextends downwardly across one end of the holder backplate between itsupper and lower flanges. The lower end of the roller shaft 21 is mountedin a bearing (not shown) which may be sup ported by the housing 12. Inthe particular portable unit disclosed. the motor 22 for the driveroller 20 is connected in series with a battery 26 through an on-offswitch 28, an on light 30 also being connected in series with the switchand battery. In view of the fact that the portable unit shown is batterypowered, means, not shown, may be provided for insuring that the carrier20 will always rotate at a constant linear speed.

The chart holder 16 is located at the rear of the housing 12 in aposition readily visible to the pilot of the aircraft. Supported by thebackplate of the holder 16 so as to be movable by the roller 20 in thedirection of the arrow in FIG. 1 is an interchangeable chart or card 32having a rectangular shape extending from A to A lengthwise and from Bto B crosswise. On this chart 32 is a curved line 34 which indicatesnormal takeoff acceleration versus takeoff time for the particularaircraft under a particular set of conditions, such as aircraft weight,airport runway, wind velocity and direction, barometric pressure. andthe like. If desired, the line 34 may be established experimentally forthe particular aircraft and set of conditions. Alternatively, a suitableset of charts may be made up from flight test data sufficient toestablish the takeoff performance of the airplane throughout theexpected range of operating conditions.

The chart 32 also is provided with a horizontal straight line 36 belowthe curved line 34 which represents zero acceleration. The shaded area38 between the zero acceleration line 36 and the normal takeoffacceleration line 34 is electrically conductive and represents an areaof subnormal acceleration. At the right hand end of the normalacceleration line 34, the chart is provided with another electricallyconductive area 40, as indicated by additional shading, which extendsvertically across the one end thereof.

Located at a predetermined reference point on the time scale of thechart or card 32 which may be marked along its horizontal dimension isan accelerometer 42 past which the time scale is driven linearly duringtakeoff by the constant speed motor 22. It will be understood that theswitch 28 is closed to energize the motor 22 at the start of takeoff,with the zero point on the time scale located opposite the accelerometer42.

The accelerometer 42 shown comprises a pendulum 44 connected to an arm46 having thereon a pivoted arm 48 carrying a pointer 50 engageable withthe chart 32, and biased into engagement therewith by a spring 52. Aswill be apparent, during takeoff acceleration in the direction of thearrow 18, the pendulum 44 causes the pointer 50 to move vertically orcross wise on the chart 32 as the latter moves horizontally at aconstant rate. The pointer follows the normal acceleration line 34 ifthe takeoff acceleration of the aircraft is normal. Preferably, underconditions of zero acceleration, the pendulum 44 is in an inclinedposition against a stop 54, as shown in FIG. 2. This insures against anymovement of the pendulum 44 prior to the actual beginning of the takeoffrun. However, the pendulum 44 may hang vertically under conditions ofzero acceleration if desired.

The pointer 50, as best shown in FIG. 4, comprises electrical contacts56 electrically insulated from each other and connected in series withthe battery 26 through a warning indicator 58, which may be a warninglight, as shown, a buzzer, or any other suitable indicator.

Considering the operation of the abort indicator 10, the appropriateacceleration card or chart 32 is first placed in the holder so as to beproperly positioned and engaged by the drive roller 20. By means of theknob 29 the pointer is initially located at one end of the area 38formed by the acceleration curve 34. The indicator 10 is turned on atthe moment the takeoff is started. In the particular constructionillustrated, this is accomplished by closing the switch 28 manually.However, means, not shown, may be provided for starting the operation ofthe abort indicator l0 automatically in response to initiation of thetakeoff run.

The accelerometer 42 responds to the takeoff acceleration experienced bythe aircraft and, if the acceleration during the takeoff run is normal,the pointer 50 follows the normal acceleration line 34 as the chart 32is moved linearly by the drive roller 20. If the acceleration is belownormal, or drops below normal, for any reason, the pointer movesdownwardly into the electrically conductive area 38, thereby causing abridging of the contacts 56 to energize the warning indicator 58.Momentary energizations of the warning indicator 58 may not be of anysignificance and can be ignored by the pilot. However, if the warningindicator 58 is energized during the takeoff run for an appreciablelength of time, the pilot should abort the takeoff.

The additional electrically conductive area 40 at the end of the card 32provides a safety factor which warns the pilot that the abort point hasbeen reached on the basis of time alone. even though the accelerationhas been normal. If for any reason the aircraft has not become airborne,or is not about to become airborne, when the electrically conductivearea 40 reaches the pointer 50, the warning indicator 58 is energized toadvise the pilot to abort immediately.

As will be apparent, the abort indicator requires relatively littleattention from the pilot during takeoff since it can be placed in aposition wherein the warning indicator 58 is readily visible in theevent that it is a light, as shown. Alternatively, or additionally, thewarning indicator 58 may provide an audible warning, thereby requiringno visual attention from the pilot during takeoff.

In FIG. 5 of the drawing is shown an alternative accelerometer 60 whichincludes a mass 62 acting on a pressure sensitive resistor 64. Thelatter is connected through an on-off switch 66 and a battery 68 to asolenoid 70 having an armature 72 the position of which is determined bythe acceleration controlled resistance in the resistor 64. The armature72 is connected to an arm 74 which carries a spring loaded arm 76 andpointer 78 similar to the spring loaded arm 48 and pointer 50. Thepointer 78, of course, engages the chart 32 within the holder 16 toindicate the magnitude of the actual takeoff acceleration at anyinstant.

FIG. 6 shows a similar accelerometer wherein a mass actuated condenser80 is used in an accelerometer cir cuit similar to that of FIG. 5.

While the abort indicator 10 has been described solely in connectionwith aborting takeoffs, it will be understood that it can be used inconnection with landings as well merely by rotating the indicator unit180 so that it responds to negative acceleration (deceleration). Ofcourse, charts of landing deceleration versus time must be substituted.

Although exemplary embodiments of the invention have been disclosed forpurposes of illustration, it will be understood that various changes,modifications and substitutions may be incorporated in such embodimentswithout departing from the spirit of the invention as defined by theclaims appearing hereinafter.

I claim:

1. In an aircraft takeoff abort indicator, the combination of:

a. a chart holder;

b. a chart mounted for linear movement on said holder and having arepresentation of normal takeoff acceleration versus takeoff time forthe aircraft. said chart being generally rectangular and having aconductive area representing the subnormal takeoff acceleration versustakeoff time relationship for the aircraft;

c. chart driving means for moving said chart linearly at a constant rateand thereby displacing the takeoff time scale on said chart past areference point;

d. an acceleration indicator at said reference point adapted to indicateon said chart the actual takeoff acceleration of the aircraft versustakeoff time;

e. acceleration responsive means responsive to the actual takeoffacceleration of the aircraft for actuating said acceleration indicator;

f. a warning indicator; and

g. actuating means including a contact engageable with said conductivearea and adapted to scan the normal takeoff acceleration versus takeofftime relationship on said chart as it moves linearly, and responsive tosubnormal takeoff acceleration of the aircraft, for actuating saidwarning indicator.

2. An abort indicator according to claim 1 including another conductivearea on and extending across one end of the chart at a point on the timescale indicating the maximum permissible takeoff time without aborting.

3. An abort indicator as defined in claim 2 wherein said holder is fixedand said chart has a vertical takeoff acceleration scale and ahorizontal takeoff time scale.

4. An abort indicator as defined in claim 1 wherein said chart drivingmeans is a cylindrical roller that frictionally engages said chart andmoves it linearly in the same direction as its takeoff time scale.

l i! l

1. In an aircraft takeoff abort indicator, the combination of: a. achart holder; b. a chart mounted for linear movement on said holder andhaving a representation of normal takeoff acceleration versus takeofftime for the aircraft, said chart being generally rectangular and havinga conductive area representing the subnormal takeoff acceleration versustakeoff time relationship for the aircraft; c. chart driving means formoving said chart linearly at a constant rate and thereby displacing thetakeoff time scale on said chart past a reference point; d. anacceleration indicator at said reference point adapted to indicate onsaid chart the actual takeoff acceleration of the aircraft versustakeoff time; e. acceleration responsive means responsive to the actualtakeoff acceleration of the aircraft for actuating said accelerationindicator; f. a warning indicator; and g. actuating means including acontact engageable with said conductive area and adapted to scan thenormal takeoff acceleration versus takeoff time relationship on saidchart as it moves linearly, and responsive to subnormal takeoffacceleration of the aircraft, for actuating said warning indicator. 2.An abort indicator according to claim 1 including another conductivearea on and extending across one end of the chart at a point on the timescale indicating the maximum permissible takeoff time without aborting.3. An abort indicator as defined in claim 2 wherein said holder is fixedand said chart has a vertical takeoff acceleration scale and ahorizontal takeoff time scale.
 4. An abort indicator as defined in claim1 wherein said chart driving means is a cylindrical roller thatfrictionally engages said chart and moves it linearly in the samedirection as its takeoff time scale.